The present embodiment relates generally to a retarder for delaying setting of a cementing composition in a subterranean zone penetrated by a well bore.
In the drilling and completion of an oil or gas well, a cementing composition is often introduced in the well bore for cementing pipe strings. In this process, known as xe2x80x9cprimary cementing,xe2x80x9d a cementing composition is pumped into the annular space between the walls of the well bore and the pipe string. The cementing composition sets in the annular space, supporting and positioning the pipe string, and forming a substantially impermeable barrier which divides the well bore into subterranean zones. After primary cementing, the undesirable migration of fluids between zones is prevented. Likewise, cementing compositions are often subsequently introduced into a subterranean zone for remedial operations to recover circulation or to plug the well bore.
Regardless of the motivation for introducing the cementing composition into a subterranean zone (xe2x80x9ccementing operationsxe2x80x9d), with relatively hot or deep well bores it is often necessary to add a component, known as a xe2x80x9cretarder,xe2x80x9d to the cementing composition to slow setting, thereby increasing pumping time. A variety of factors affect the effectiveness of a retarder, including settling tendencies, environmental friendliness, and temperature range. For example, retarders are usually considered as those suitable for use at 100-200xc2x0 F. and retarders suitable for use at 200-300xc2x0 F. These temperatures are based on downhole temperature measured while circulating fluid in the well bore, known as the bottomhole circulating temperature (xe2x80x9cBHCTxe2x80x9d).